At least two different monomers can be polymerized in the same polymerization system so as to generate a copolymer having those different monomer units arranged as repeating units in one polymer chain, and the copolymer thus obtained can be classified into a random copolymer, an alternating copolymer, a block copolymer, or a graft copolymer, depending on the arrangement of the monomer units. However, no report has been made on the arrangement of monomer units in polymerization reaction of a conjugated diene compound and a non-conjugated olefin.
For example, JP 2000-154210 A (PTL 1) discloses a catalyst for polymerization of a conjugated diene, the catalyst including a group IV transition metal compound which has a cyclopentadiene ring structure, in which an α-olefin such as ethylene is exemplified as a monomer copolymerizable with the conjugated diene. However, no reference is made on the arrangement of monomer units in the copolymer. Further, JP 2006-249442 A (PTL 2) discloses a copolymer of an α-olefin and a conjugated diene compound, but no reference is made on the arrangement of monomer units in the copolymer. Further, JP 2006-503141 A (PTL 3) discloses an ethylene/butadiene copolymer synthesized by using a catalytic system consisting of a specific organometallic complex, but merely describes that the butadiene as a monomer is inserted in the form of trans-1,2-cyclohexane into the copolymer, without making any reference to the arrangement of monomer units in the copolymer. It goes without saying that no reference or indication is made as to the manufacture of a rubber which includes monomer units arranged in a tapered structure in the copolymer to thereby obtain an excellent heat resistance and flex fatigue resistance.
In addition, JP 11-228743 A (PTL 4) discloses an unsaturated elastomer composition composed of an unsaturated olefin-based copolymer and a rubber, but merely describes that monomer units in the copolymer are randomly arranged. It goes without saying that no reference or indication is given as to the manufacture of a rubber which includes monomer units arranged in a tapered structure in the copolymer to thereby obtain an excellent heat resistance and flex fatigue resistance.